The adulteration of critical use articles such as surgical gloves and condoms poses considerable health risks. Adulteration as used herein is intended to encompass conditions such as holes formed during manufacture of the article as well as holes formed thereafter for any reason, which holes provide a path for adulteration of the article by potentially dangerous fluids such as body fluids. The term "holes" or "perforations" includes not only holes capable of initially passing fluid but also incipient holes, which may, initially, be too small to pass amounts of fluid but may enlarge over time, or otherwise breach or deteriorate the integrity of the barrier posed by the article. Such holes may even form a danger before reaching a size large enough to pass actual fluid since bacteria may theoretically pass through even smaller openings; but, it is more likely that a fluid carrier is needed to carry the bacteria through the membrane.
One example of a critical use article is the surgical glove. Although problems associated with surgical gloves are discussed below, it is understood that similar problems are presented by other articles such as condoms, surgical gowns, surgical drapes, etc. The adulteration of gloves used in surgery has long been a problem to the medical doctor or other health care worker. There are two common sources for the creation of holes or perforations in surgical gloves prior to and during use. One source is the manufacturer who, due to lack of quality control or inherent manufacturing problems, may manufacture and sell gloves which already have perforations. In about 1990, the Federal Food and Drug Administration has determined, by field inspection, failure rates of three to sixteen percent in surgical gloves prior to use. The FDA further found that, for patient-examination gloves, average defect rates range from fourteen to eighteen percent. In a recent attempt to tighten the quality control in surgical gloves, the FDA has resorted to its own modification of the well-known and fundamental A.S.T.M. technique for determining defects in gloves--a water fill test. The water fill test is only capable of detecting holes large enough to pass visually detectable amounts of water. Danger exists when a hole is large enough to expose skin on the other side of the glove to harmful bacteria or virus even though the hole may not be large enough to actually allow visible amounts of water to pass through the hole during the water fill test.
The second source of holes or perforations in gloves occurs during use. For example, holes or dangerously thin spots may develop in gloves at the time that the surgeon first fits the gloves over his or her hands, or, a glove may be perforated during surgery. Perforations during surgery can occur because of penetration by sharp objects or because of the breaking down of inherently thin spots in the gloves or areas made thin as a result of putting the glove on the hand or manipulating instruments. Perforations expose the surgeon to actual or possible contact with patient body fluids because of the resulting adulteration of the surgical gloves. While such adulteration has always been a possible source of infection or the spreading of bacteria to the surgeon or from the surgeon to the patient, the alarming spread of the hepatitis and AIDS viruses has created an even more serious problem--the possible spread of an incurable disease from the patient to the surgeon or from the surgeon to the patient. Therefore, the need for accurate and immediate detection of actual or near-adulteration in surgical gloves is now at a heightened level because of the potential for the spread of incurable diseases from patient to surgeon or vice-versa.
The problem with the AIDS virus is not limited, however, to surgeons or other persons in the operating room such as nurses and anesthesiologists. For example, it is possible that other users of critical use gloves such as dentists or paramedics may be subject to many of the same serious concerns because the dentist or paramedic is also exposed to body fluids during his or her work on a patient. While perhaps less likely, there is also some possibility for the spread of serious diseases from patients to doctors during physical examinations. For purposes of definition, doctors, dentists, nurses and others who may be exposed to disease through gloves or other barriers are defined herein as "health care workers." It is also noted that the problem of communication of a disease between persons due to adulteration of a material acting as a barrier between the persons is not limited to surgical gloves, but other articles such as surgical gowns, masks and condoms present similar problems.
While the FDA has taken the approach of using the rudimentary method of simple water fill to determine leaks in gloves as manufactured, such simple techniques cannot be used to detect adulteration in gloves during use. There have been some attempts in the prior art to detect the occurrence of perforations in surgical gloves after the gloves are on the doctor's hands, all of which use resistance level detection as the parameter to detect holes. Such level detection concepts have been known for several decades and recently there have been further efforts at modest improvement on such detection mechanisms, all continuing to rely on resistance level detection as the principal parameters to be measured.
U.S. Pat. No. 4,321,925 of John Hoborn and Ulrich Krebs discloses an electronic detector arranged so that the level of electronic conductivity through the gloves and between the patient and the surgeon may be sensed at regularly recurring discrete time intervals in order to measure a predetermined level of sensed conductivity and signal an alarm if such predetermined level is met. The detecting circuit of the '925 patent is actually located in one of the shoes of the surgeon and includes one contact located in the insole of the shoe in order to make electrical contact with the surgeon and a second contact exposed to an electrically conducting plate located on the floor of the operating room so that a closed circuit is formed between the operating table, the patient, the doctor, the electronic device located in the shoe and the round conducting element or plate located on the floor of the operating room. The '925 patent teaches that five times per second the disclosed circuit short-circuits the contacts in the insole and in the bottom of the sole of the shoe in order to discharge static electricity from the insole contact which may have accumulated from the doctor. After each short circuit, the circuit is opened between the two contacts and a voltage level sensor is used to detect the level of electrical conductivity which occurs externally between the contacts.
The impedance of the rubber or latex that comprises the surgical gloves is high. If there is a perforation in the operating gloves of the surgeon, the impedance is thereby reduced and a greater conductivity is provided through the gloves. The '925 patent teaches that the occurrence of a perforation in the operating gloves may result in a relatively high electric conductivity between the surgeon and patient, thus allowing the sensing device to sound an alarm upon the occurrence of a predetermined level of sensed conductivity.
Setting of the appropriate level of conductivity is strictly a matter of design and thus it is believed that one drawback to the device of the '925 patent is that the level of conductivity required to trigger the alarm may differ from glove to glove, depending upon the nature of the material, the thickness of the material and any other factors which may impact upon the general conductivity of the series circuit, which includes not only the doctor and patient, but also the doctor's shoes, a round plate located on the operating floor, and the operating table itself. Therefore, the '925 patent may work fairly well for certain types of gloves whose characteristics conform to the particular resistance level chosen for the resistance level sensor, but the '925 patent may not work well with many other types of gloves. In order to function properly, the resistance level sensor in the '925 patent would have to be adjusted to some pre-determined level depending on the type of gloves used.
Perhaps more importantly, the tendency of latex gloves to absorb fluid during use is a factor not solved by the '925 Hoborn patent and other similar resistance level detection devices. Most natural rubber latex gloves absorb considerable quantities of water with time, referred to as hydration. This hydration effect causes the conductivity of the glove to increase markedly, thus decreasing its resistance. Eventually, the electrical resistance of the gloves becomes as low as a glove with a hole in it. Thus for many types of surgeons' gloves, devices like that shown in the '925 patent will eventually give a hole alarm when there is no perforation. Therefore, the fact that the absolute conductivity of a glove varies with the hydration of the glove material detracts from the effectiveness of the sensor of the '925 device. There are other patents which disclose level detection type devices which are believed to have disadvantages similar to the '925 patent. See U.S. Pat. Nos. 4,956,635 of Langdon and 5,036,309 of Dennison.
Other prior art devices include several devices that utilize a basin of conductive fluid in which the surgeon places his or her gloved hands for the purposes of determining whether or not the gloves have become adulterated. See U.S. Pat. Nos. 2,981,886 of Beck; 4,810,971 of Marable; 4,909,069 of Albin; and 4,956,635 of Langdon. If the conductive fluid in the basin enters a gloved hand or comes in contact with body fluid already in the adulterated glove, increased conductivity is detected. Other devices and relevant prior art are discussed in an Information Disclosure Statement.
It is submitted that there is need for the development of further, more sophisticated detection methods and apparatus in order to detect adulteration of surgical or other critical use gloves. This detection method should also preferably not interfere with the normal activities of the user. In addition, there is a need for detection methods which do not necessarily depend on the absolute level of conductivity of particular gloves, but are capable of detecting rapid changes in glove condition. Also, it is desirable for the detection method to be able to reliably monitor the integrity of gloves for an extended period of time and to be adaptable to different glove types from different glove manufacturers.
One solution is found in the parent patent application Ser. No. 07/528,926, which teaches a technology of detection of the rate of change of electrical properties in barriers such as critical use surgical gloves.